Clinical characteristics, cause analysis and infectivity of COVID-19 nucleic acid repositive patients: A literature review

Advances in Nucleic Acid Assays for Infectious Disease: The Role of Microfluidic Technology

Within the fields of infectious disease diagnostics, microfluidic-based integrated technology systems have become a vital technology in enhancing the rapidity, accuracy, and portability of pathogen detection. These systems synergize microfluidic techniques with advanced molecular biology methods, including reverse transcription polymerase chain reaction (RT-PCR), loop-mediated isothermal amplification (LAMP), and clustered regularly interspaced short palindromic repeats (CRISPR), have been successfully used to identify a diverse array of pathogens, including COVID-19, Ebola, Zika, and dengue fever. This review outlines the advances in pathogen detection, attributing them to the integration of microfluidic technology with traditional molecular biology methods and smartphone- and paper-based diagnostic assays. The cutting-edge diagnostic technologies are of critical importance for disease prevention and epidemic surveillance. Looking ahead, research is expected to focus on increasing detection sensitivity, streamlining testing processes, reducing costs, and enhancing the capability for remote data sharing. These improvements aim to achieve broader coverage and quicker response mechanisms, thereby constructing a more robust defense for global public health security.

Changes of gut microbiota under different nutritional methods in elderly patients with severe COVID-19 and their relationship with prognosis

Background

The clinical progression of individuals afflicted with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection exhibits significant heterogeneity, particularly affecting the elderly population to a greater extent. Consequently, the association between nutrition and microbiota has garnered considerable interest. Hence, the objective of this study was to gather clinical data pertaining to the influence of diverse nutritional support interventions on the prognosis of geriatric patients with COVID-19, while additionally examining the fecal microbiota of these individuals to assess the repercussions of microecological alterations on their prognostic outcomes.

Results

A total of 71 elderly patients diagnosed with severe COVID-19 were included in this study. These patients were subsequently divided into two groups, namely the enteral nutrition (EN) group and the parenteral nutrition (PN) group, based on the type of nutritional support therapy they received after admission. The occurrence of complications was observed in 10.4% of patients in the EN group, whereas it was significantly higher at 69.6% in the PN group (P<0.001). Furthermore, the 60-day mortality rate was 2.1% (1/48) in the EN group, while it was notably higher at 30.4% (7/23) in the PN group (P=0.001). To identify the independent predictors of 60-day mortality, stepwise logistic regression analysis was employed. Among different bacterial groups, Enterococcus_faecium (18.19%) and Pseudomonas_aeruginosa (1.91%) had higher average relative abundance in the PN group (P<0.05). However, the relative abundance of Ruminococcus was higher in the EN group. Further Spearman correlation analysis showed that Enterococcus_faecium was positively correlated with poor clinical prognosis, while Ruminococcus was negatively correlated with poor clinical prognosis.

Conclusions

This study shows that the changes in the composition of intestinal flora in elderly COVID-19 patients receiving different nutritional support strategies may be related to different clinical outcomes. The abundance of Enterococcus_faecium in elderly COVID-19 patients receiving PN is significantly increased and is closely related to poor clinical outcomes. It highlights the potential of microbiome-centric interventions to mitigate and manage COVID-19 in older adults with different nutritional support options.

Risk Factors and Disease Profile Associated with the Nucleic Acid Conversion Time of COVID-19 Patients Infected with the SARS-CoV-2 Omicron Variant in Fangcang Shelter Hospitals

Purpose

This study aimed to determine the clinical profile connected to the nucleic acid conversion time of COVID-19 patients harboring the SARS-CoV-2 Omicron variant at the hospitals at the Fangcang shelter.

Methods

We reported 39,584 COVID-19 patients who were hospitalized in Shanghai, China, between April 5 and May 5, 2022, and who had contracted the Omicron strain of SARS-CoV-2. Demographic data, medical and vaccination history, clinical symptoms, and NCT were reported for the patient.

Results

The median age of the patients with COVID-19 included in this study was 45 (interquartile range [IQR]: 33-54), and 64.2% of them were male. The two most prevalent comorbidities among the patients were hypertension and diabetes. Additionally, we discovered that the percentage of unimmunized patients was negligible (13.2%). We found that male sex, age under 60, and other comorbidities including hypertension and diabetes are significant risk factors for extending NCT when we analyzed the risk variables for NCT. We discovered that vaccination with two or more doses can significantly reduce NCT. The analysis of the young (18-59 years) and older (60 years) populations produced the same outcomes.

Conclusion

Our findings confirm that a full COVID-19 vaccine series or booster doses are highly recommended to significantly reduce NCT. In order to reduce NCT, it is also advised that elderly people who have no clear contraindications take vaccination shots.

Genetic predisposition between coronavirus disease 2019 and rheumatic diseases: A 2-sample Mendelian randomization study

OBJECTIVE

The causalities between the coronavirus disease 2019 (COVID-19) and the risk of rheumatic diseases remain unclear. The purpose of this study was to investigate the causal effect of COVID-19 on rheumatic disease occurrence.

METHODS

Single nucleotide polymorphisms (SNPs), acquired from published genome-wide association studies, were used to perform 2-sample Mendelian randomization (MR) on cases diagnosed with COVID-19 (n = 13 464), rheumatic diseases (n = 444 199), juvenile idiopathic arthritis (JIA, n = 15 872), gout (n = 69  374), systemic lupus erythematosus (SLE, n = 3094), ankylosing spondylitis (n = 75 130), primary biliary cholangitis (PBC, n = 11 375) and primary Sjögren's syndrome (n = 95 046). Three MR methods were used in the analysis based on different heterogeneity and pleiotropy using the Bonferroni correction.

RESULTS

The results revealed a causality between COVID-19 and rheumatic diseases with an odds ratio (OR) of 1.010 (95% confidence interval [CI], 1.006-1.013; P = .014). In addition, we observed that COVID-19 was causally associated with an increased risk of JIA (OR 1.517; 95%CI, 1.144-2.011; P = .004), PBC (OR 1.370; 95%CI, 1.149-1.635; P = .005), but a decreased risk of SLE (OR 0.732; 95%CI, 0.590-0.908; P = .004). Using MR, 8 SNPs were identified to associate with COVID-19 and recognized as significant variables. None of them were previously reported in any other diseases.

CONCLUSIONS

This is the first study to use MR to explore the impact of COVID-19 on rheumatic diseases. From a genetic perspective, we found that COVID-19 could increase the risk of rheumatic diseases, such as PBC and JIA, but decrease that of SLE, thereby suggesting a potential surge in the disease burden of PBC and JIA following the COVID-19 pandemic.

Effect of SARS CoV-2 Infection on Periodontal Tissue: A Systematic Review

Background:

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) infection in human respiratory cells. The first spread of this disease first occurred in Wuhan, China, in December 2019, and on March 11, 2020, the World Health Organization declared the spread of the infection as a global pandemic. People who are infected experience mild to moderate clinical symptoms which are characterized by an increase in T cell, CD8, and IgM/IgG levels. The occurrence of severe clinical symptoms reflects an excessive and uncontrolled increase in the secretion of pro-inflammatory cytokines, which impacts the systemic condition and periodontal tissues of affected patients.

Objective:

The aim of this study is to describe the impact of SARS CoV-2 infection on periodontal tissues.

Methods:

In this study, we searched the NCBI, PubMed, Google Scholar, and Research Gate databases. The keywords used were “coronavirus disease” or “COVID-19” or “SARS-CoV-2” with “oral manifestations” and “periodontal,” and we screened the articles using the PRISMA flow diagram.

Results:

Patients with COVID-19 present with a variety of systemic symptoms, as well as manifestations in the periodontal tissues, especially in the gingival area.

Conclusion:

SARS CoV-2 infection can impact periodontal tissues in the form of necrotizing ulcerative gingivitis, aphthous stomatitis, gingival hyperpigmentation, edema and erythema, lichen planus, and aphthous-like ulcers.

ACE2 in male genitourinary and endocrine systems: Does COVID-19 really affect these systems?

The virus that causes COVID-19 (Corona Virus Disease 2019), SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2), is causing a worldwide pandemic, posing a substantial threat to human health. Patients show signs of pneumonia, ARDS, shock, acute cardiac injury, acute kidney injury and other complications. The SARS-CoV-2 receptor is angiotensin converting enzyme 2 (ACE2), which is an important component of the renin-angiotensin system (RAS). In addition, TMPRSS2 or other cofactors are needed to allow the virus to enter the host. Clinical patients have exhibited varying degrees of genitourinary and endocrine system damage, and some studies have also reported potential risks to the genitourinary and endocrine systems. This article reviews the mechanism underlying SARS-CoV-2 infection and the current studies on the male genitourinary and endocrine systems and proposes that more attention should be directed towards human reproductive and endocrine health during the SARS-CoV-2 epidemic.

The significant value of sustainable cosmetics fragrance in the spotlight after COVID-19

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic has brought major changes to the world's population. This has led to increased wearing of masks to prevent infectious diseases, which can contribute to exacerbation of stress and the emergence of mental illness due to a physical health crisis.

OBJECTIVES

Therefore, this study comprehensively investigated the reasons why cosmetics customers pay attention to sustainable fragrances after COVID-19.

METHODS

This review article is a literature review, and a narrative review approach was used in this study. A total of 598 references were selected from 2004 to 2022 using representative journal search sites such as PubMed, Google Scholar, Scopus, and RISS. Among them, a total of 39 articles were successfully completed in this study using the PRISMA flowchart in the final stage.

RESULTS

In this study, by identifying the changes and needs of K-beauty and global cosmetics industry consumers who aspire for sustainable safety amid the COVID-19 pandemic, the increase in bad breath caused by the increase in mask wearing was recognized, and the need for fragrance due to mental health was recognized. Demand is expected to increase.

CONCLUSION

This study tried to change the perception of cosmetic fragrances into safe edible fragrances. Therefore, it is expected to be used as an important marketing material for the global cosmetics market.

The machine learning model based on trajectory analysis of ribonucleic acid test results predicts the necessity of quarantine in recurrently positive patients with SARS-CoV-2 infection

Background

SARS-CoV-2 patients re-experiencing positive nucleic acid test results after recovery is a concerning phenomenon. Current pandemic prevention strategy demands the quarantine of all recurrently positive patients. This study provided evidence on whether quarantine is required in those patients, and predictive algorithms to detect subjects with infectious possibility.

Methods

This observational study recruited recurrently positive patients who were admitted to our shelter hospital between May 12 and June 10, 2022. The demographic and epidemiologic data was collected, and nucleic acid tests were performed daily. virus isolation was done in randomly selected cases. The group-based trajectory model was developed based on the cycle threshold (Ct) value variations. Machine learning models were validated for prediction accuracy.

Results

Among the 494 subjects, 72.04% were asymptomatic, and 23.08% had a Ct value under 30 at recurrence. Two trajectories were identified with either rapid (92.24%) or delayed (7.76%) recovery of Ct values. The latter had significantly higher incidence of comorbidities; lower Ct value at recurrence; more persistent cough; and more frequently reported close contacts infection compared with those recovered rapidly. However, negative virus isolation was reported in all selected samples. Our predictive model can efficiently discriminate those with delayed Ct value recovery and infectious potentials.

Conclusion

Quarantine seems to be unnecessary for the majority of re-positive patients who may have low transmission risks. Our predictive algorithm can screen out the suspiciously infectious individuals for quarantine. These findings may assist the enaction of SARS-CoV-2 pandemic prevention strategies regarding recurrently positive patients in the future.

Milder symptoms and shorter course in patients with re-positive COVID-19: A cohort of 180 patients from Northeast China

China experienced another widespread Coronavirus disease 2019 (COVID-19) outbreak recently caused by the Omicron variant, which is less severe but far more contagious than the other COVID-19 variants, leading local governments to focus efforts on eliminating the spread of the disease. Previous studies showed that after “recovering” from the virus, some patients could re-test positive for COVID-19 with nucleic acid tests, challenging the control of disease spread. In this study, we aimed to analyze the clinical and laboratory characteristics of re-positive COVID-19 patients in Northeast China. We retrospectively analyzed data from confirmed reverse transcription polymerase chain reaction (RT-PCR) re-positive COVID-19 patients who were admitted to the First Hospital of Jilin University, Jilin Province, China, from March to June 2022. Detailed clinical symptoms, medical history, anti-Corona Virus (CoV) IgG and IgM levels, and CoV nucleic acid cycle threshold (Ct) values during the re-positive period were collected and analyzed. A total of 180 patients were included in this study, including 62 asymptomatic cases and 118 mild cases. The cohort included 113 men and 67 women, with an average age of 45.73 years. The median time between recovery from the virus and re-positivity was 13 days. Our results showed that the proportion of re-positive patients with symptoms was lower, and the nucleic acid test-positive duration was shorter during the re-positive period. Furthermore, in patients with underlying disease, the proportion of patients with symptoms was higher, anti-CoV IgG levels were lower, and the total disease duration was longer. In conclusion, during the re-positive period, the symptoms were milder, and the CoV nucleic acid test-positive course was shorter. The concomitant underlying disease is an important factor associated with clinical symptoms, and the overall course of COVID-19 re-positive patients may be associated with lower anti-CoV IgG levels. Large-scale and multicenter studies are recommended to better understand the pathophysiology of recurrence in patients with COVID-19.

SARS-CoV-2 indoor environment contamination with epidemiological and experimental investigations

SARS-CoV-2 has been detected both in air and on surfaces, but questions remain about the patient-specific and environmental factors affecting virus transmission. Additionally, more detailed information on viral sampling of the air is needed. This prospective cohort study (N = 56) presents results from 258 air and 252 surface samples from the surroundings of 23 hospitalized and eight home-treated COVID-19 index patients between July 2020 and March 2021 and compares the results between the measured environments and patient factors. Additionally, epidemiological and experimental investigations were performed. The proportions of qRT-PCR-positive air (10.7% hospital/17.6% homes) and surface samples (8.8%/12.9%) showed statistical similarity in hospital and homes. Significant SARS-CoV-2 air contamination was observed in a large (655.25 m³ ) mechanically ventilated (1.67 air changes per hour, 32.4-421 L/s/patient) patient hall even with only two patients present. All positive air samples were obtained in the absence of aerosol-generating procedures. In four cases, positive environmental samples were detected after the patients had developed a neutralizing IgG response. SARS-CoV-2 RNA was detected in the following particle sizes: 0.65-4.7 μm, 7.0-12.0 μm, >10 μm, and <100 μm. Appropriate infection control against airborne and surface transmission routes is needed in both environments, even after antibody production has begun.

Sickle cell disease patients with COVID‐19 in Guadeloupe: Surprisingly favorable outcomes

We investigate risk factors for hospitalization and difference between sickle cell syndromes in a cohort of COVID‐19 sickle cell disease (SCD) adult patients managed in the Reference Center of Guadeloupe. We retrospectively collected data of symptomatic SCD adult patients infected with SARS‐CoV‐2 between March and December 2020. Thirty‐eight SCD adult patients with symptomatic COVID‐19 infection were included during the first wave, representing 9.6% of the active patient file at our center. The median age (IQR) was 39 years (24–47). Four patients were obese and two had moderate renal failure. The median duration of symptoms (IQR) was 10 days (5–15). Seventeen (44.7%) patients were hospitalized, including two in intensive care unit (ICU) for acute chest syndrome. An 85‐year‐old SC patient with prostate cancer died. No difference was detected between inpatient and outpatient groups in terms of age, gender, BMI, SCD clinical complications, and in history SCD treatment. There was no difference for severity, hospitalization, length of stay, ICU stay, or death between SS or Sβ°‐thal patients and SC or Sβ⁺‐thal patients. These overall favorable outcomes among symptomatic patients may be related to the low prevalence of comorbidity known to be linked to the more severe forms of COVID‐19, but also to the prompt coordinated management of SCD patients in the Reference Center.

Delayed Diagnosis and Multi-TKI Intolerance: A Case Report of CML Concurrent With COVID-19

Introduction

The hematological manifestations of corona virus disease 2019 (COVID-19) can confound the diagnosis and therapy of other diseases. In this paper, we firstly reported a case of chronic myeloid leukemia (CML) of delayed diagnosis and intolerance to tyrosine kinase inhibitors (TKIs) concurrent with COVID-19.

Case Presentation

A 56-year-old female was diagnosed as COVID-19 with no obvious leukocytosis [white blood cell (WBC), ≤17 × 10⁹/L] or splenomegaly until ablation of the virus. Bone marrow aspiration was conducted to establish the diagnosis of CML. She accepted an adjusted dosage of imatinib initially and had to suspend it after myelosuppression (day 41). After hematopoietic therapy, imatinib was given again (day 62), but she was still non-tolerant, and nilotinib at 150 mg twice a day was prescribed from day 214. At just about 4 weeks later, nilotinib was discontinued due to myelosuppression. Then, it was reduced to 150 mg per day and was re-initiated (day 349), but she was still non-tolerant to it. Similarly, from day 398, flumatinib at 200 mg per day was tried, but she was non-tolerant. Her white blood cell or platelet count fluctuated markedly with poor therapeutic response. Considering that she was relatively tolerant and responsive to imatinib, the medication was re-initiated at 200 mg and reduced to 100 mg per day. Her follow-up revealed stable WBC and PLT counts. The latest BCR-ABL-210/ABL was decreased to 0.68% at about 6 months after imatinib was re-initiated, which means an improved response.

Conclusion

The offset effect between CML and SARS-CoV-2 infection was supposed to be the underlying mechanism for the absence of leukocytosis or splenomegaly. The impact of immune network by SARS-CoV-2 preserved and disrupted the patient’s response to TKIs despite the virus’ ablation. We suggest that a continued elevation of basophils may be a useful indicator for CML concurrent with COVID-19, and individualized treatment with adjusted dosage and suitable type of TKIs should be considered to improve the patient’s health outcome.

Analysis of 4 cases of children with false-positive results of novel coronavirus-specific antibody

Background

This study attempts to explore the influencing factors and solutions of the colloidal gold method for novel coronavirus (2019-nCoV)-specific IgM/IgG antibody detection, summarize the clinical experience and perfect the examination process, improving the application value of antibody detection in COVID-19 diagnosis.

Methods

A total of 13,329 peripheral whole blood/plasma/serum samples were obtained for COVID-19 screening from children who visited the Children's Hospital of the Capital Institute of Pediatrics outpatient clinic from April 22, 2020, to November 30, 2020. The colloidal gold method was adopted for 2019-nCoV-specific IgM/IgG antibody detection. The virus nucleic acid test results, clinical records, and serum protein fingerprint results of antibody-positive patients were collected.

Results

All samples were examined using the colloidal gold method with two 2019-nCoV-specific IgM/IgG antibody detection kits. Four patients were tested single antibody-positive using both kits. The details were as follows: two cases of IgM ( +) and IgG (-) using plasma and serum separately, two cases of IgM (-) and IgG ( +) using serum and whole blood. The protein fingerprinting results and nucleic acid tests of 2019-nCoV antibodies were negative in the 4 cases. Considering the epidemiological history, clinical manifestations, and test results, these 4 children were ruled out for 2019-nCoV infection.

Conclusions

When the colloidal gold method was used to detect 2019-nCoV-specific IgM/IgG antibodies, it was important to ascertain the test results as precisely as possible. Specimen type and patient history may interfere with the diagnosis.

Establishment of primary health information in the COVID-19 outbreak: A cross-sectional study of population awareness of self-testing

The global pandemic of the Corona Virus Disease 2019 is a severe threat to human health. This paper aims to investigate the status of mass health self-examination awareness and its influencing factors during the COVID-19 epidemic and establish complete health information to intervene in the prevention and control of the COVID-19 epidemic. The study used a simple random sampling method to survey permanent residents (9761 people) aged 15–70 years in a region of Jiangsu Province, China. The survey collected data using a questionnaire with acceptable reliability and validity. The data were entered into SPSS 26, and the data were analyzed using the chi-square test, ANOVA, and logistic regression. The differences in the status of mass health self-examination during COVID-19 were statistically significant (P < 0.05) in terms of the literacy level of the grassroots population, ease of access to medical care, primary medical and health conditions, the situation of medical examination programs, and the construction of primary health information technology. The establishment of comprehensive and systematic primary health information can effectively assist in raising people's awareness of health self-examination and promoting health behaviors, which is essential for enhancing COVID-19 prevention and intervention.

Predictive Value of Systemic Immune-Inflammation index and Neutrophil-to-Lymphocyte Ratio in Patients with Severe COVID-19

Objective: It was initially reported that a novel coronavirus (COVID-19) had been identified in Wuhan, China, in December 2019.To date, COVID-19 is still threatening all humanity and has affected the public healthcare system and the world economic situation. Neutrophil-to-lymphocyte ratio (NLR) has also been demonstrated that associated with severity of COVID-19, but little is known about systemic immune-inflammation index (SII) relation with COVID-19. Methods: One hundred and twenty-five patients with diagnosed COVID-19 including non-severe cases (n = 77) and severe cases (n = 48) were enrolled in this study. Each patient of clinical characteristic information, blood routine parameters, and the haemogram-derived ratios were collected, calculated, and retrospectively analyzed. Receiver operating characteristics (ROC) was performed to investigate whether these parameters could be used to the predictive value of patients with severe COVID-19. Results: White blood cell count (WBC), neutrophil count (NEU), red cell volume distribution width (RDW), NLR, Platelet to lymphocyte ratio (PLR), neutrophil-to-platelet ratio (NPR), and SII were significantly higher in the severe groups than in the non-severe group (p < 0.01).Conversely, the severe group had a markedly decreased lymphocyte count, basophil (Baso#) count, red blood cell count (RBC), Hemoglobin (HGB), hematocrit (HCT), and lymphocyte-to-monocyte ratio (LMR) (P < 0.01).ROC curve analysis showed the AUC, optimal cut-off value, sensitivity, specificity of NLR and SII to early predict severe-patients with COVID-19 were 0.867, 7.25, 70.83%, 92.21% and 0.860, 887.20, 81.25%, 81.82%, respectively. Conclusion The results suggest that the SII and NLR is a potential new diagnosed biomarker in severe-patients with COVID-19.

Factors Associated with SARS-CoV-2 Repeat Positivity — Beijing, China, June–September 2020

Introduction

Repeat positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) following COVID-19 initial viral clearance (re-positivity) poses a public health management challenge. The objective was to determine factors associated with neutralizing antibody (Nab) level and re-positivity among patients infected with a single strain SARS-CoV-2.

Methods

During a single strain SARS-CoV-2 cluster in Beijing, China, longitudinal individual clinical, virological, and immunological data were collected from 368 infections from June 13 to September 22, 2020. Factors associated with Nab level and re-positivity were analyzed using generalized estimating equations.

Results

A total of 353 (96%) SARS-CoV-2 infections had demographic, clinical, and laboratory data available. Among the 353 infections, 55 (15.5%) were re-positive, and blood draws were taken from 346 individuals (98.0%) during hospitalization and/or during the follow-up period. Symptoms were milder for the second-time admission for the re-positives, although 36.4% of re-positives presented with radiographic appearance of pneumonia manifestation. Compared to non-re-positive patients, NAb titers were lower among re-positives; NAb was positively associated with clinical severity. Samples from the lower respiratory tract manifested higher viral load than that from the upper respiratory tract. Multivariable analysis showed re-positivity was positively associated with being female [odd ratio (OR)=1.7, 95% confidence interval (CI) 1.1–2.8] and being aged <18 years (OR=5.2, 95% CI 1.5–18.1); having initially asymptomatic infection (OR=13.7, 95% CI 1.6–116.3); and negatively associated with a higher NAb level (OR=0.9, 95% CI 0.5–1.7).

Conclusions

NAb may be important for sustained viral clearance. Lower respiratory tract infection was associated with higher viral load among all infections when compared to upper respiratory tract infection. Continuous lower respiratory and intermittent upper respiratory viral shedding among COVID-19 infections may occur.

Adoption of improved neural network blade pattern recognition in prevention and control of corona virus disease-19 pandemic

To explore the adoption effect of improved neural network blade pattern in corona virus disease (COVID)-19, comparative analysis is implemented. First, the following hypotheses are proposed. I: in addition to the confirmed cases and deaths, people suspected of being infected are also involved in the spread of the epidemic. II: patients who have been cured may also develop secondary infections, so it is considered that there is still a link between cured cases and the spread of the epidemic. III: only the relevant data of the previous day is used to predict the epidemic prevention and control of the next day. Then, the epidemic data from February 1st to February 15th in X province were selected as the control. The combined neural network model is used for prevention and control prediction, and the prediction results of the traditional neural network model are compared. The results show that the predictions of the daily new cases by the five neural network models have little difference with the actual value, and the trend is basically consistent. However, there are still differences in some time nodes. The errors of neural network 1 on the 6th and network 3 on the 13th are large. The accuracy of the combined neural network prediction model is high, and there is little difference between the result and the actual value at each time node. The prediction of the cumulative number of diagnoses per day of the five neural network models is also analyzed, and the results are relatively ideal. In addition, the accuracy of the combined neural network prediction model is high, and the difference between the result and the actual value at each time node is relatively small. It is found that the standard deviations of neural networks 2 and 3 are relatively high through the comparison of the deviations. The deviation means of the five models were all relatively low, and the mean deviation and standard deviation of the combined neural network model are the lowest. It is found that the accuracy of prediction on the epidemic spread in this province is good by comparing the performance of each neural network model. Regarding various indicators, the prediction accuracy of the combined neural network model is higher than that of the other four models, and its performance is also the best. Finally, the MSE of the improved neural network model is lower compared with the traditional neural network model. Moreover, with the change of learning times, the change trend of MSE is constant (P < 0.05 for all). In short, the improved neural network blade model has better performance compared with that of the traditional neural network blade model. The prediction results of the epidemic situation are accurate, and the application effect is remarkable, so the proposed model is worthy of further promotion and application in the medical field.

Prolonged presence of replication-competent SARS-CoV-2 in mildly symptomatic individuals: A report of two cases

It has been estimated that individuals with COVID-19 can shed replication-competent virus up to a maximum of 20 days after initiation of symptoms. The majority of studies that addressed this situation involved hospitalized individuals and those with severe disease. Studies to address the possible presence of SARS-CoV-2 during the different phases of COVID-19 disease in mildly infected individuals, and utilization of viral culture techniques to identify replication-competent viruses, have been limited. This report describes two patients with mild forms of the disease who shed replication-competent virus for 24 and 37 days, respectively, after symptom onset.

Sample Adequacy Control (SAC) Lowers False Negatives and Increases the Quality of Screening: Introduction of "Non-Competitive" SAC for qPCR Assays

Sample Adequacy Control (SAC) has critical analytical, clinical and epidemiological value that increases confidence in a negative test result. The SAC is an integral qPCR assay control, which ensures that all pre-analytical and analytical steps are adequate for accurate testing and reporting. As such, a negative SAC with a negative result on pathogen screen specifies that the result should be reported as inconclusive instead of negative. Despite this, many regulatory approved tests do not incorporate SAC into their assay design. Herein, we emphasize the universal value of SAC and offer for the first time, a simple technical strategy to introduce non-competitive SAC which does not interfere with the limit of detection for the screened pathogen. Integration of SAC can provide key benefits towards identifying, isolating, quarantining and contact tracing infected individuals and in turn can improve worldwide efforts in infection control.

A rapid and cost-effective multiplex ARMS-PCR method for the simultaneous genotyping of the circulating SARS-CoV-2 phylogenetic clades

Tracing the globally circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) phylogenetic clades by high-throughput sequencing is costly, time-consuming, and labor-intensive. We here propose a rapid, simple, and cost-effective amplification refractory mutation system (ARMS)-based multiplex reverse-transcription polymerase chain reaction (PCR) assay to identify six distinct phylogenetic clades: S, L, V, G, GH, and GR. Our multiplex PCR is designed in a mutually exclusive way to identify V-S and G-GH-GR clade variants separately. The pentaplex assay included all five variants and the quadruplex comprised of the triplex variants alongside either V or S clade mutations that created two separate subsets. The procedure was optimized with 0.2-0.6 µM primer concentration, 56-60°C annealing temperature, and 3-5 ng/µl complementary DNA to validate on 24 COVID-19-positive samples. Targeted Sanger sequencing further confirmed the presence of the clade-featured mutations with another set of primers. This multiplex ARMS-PCR assay is a fast, low-cost alternative and convenient to discriminate the circulating phylogenetic clades of SARS-CoV-2.

Clinical characteristics, cause analysis and infectivity of COVID-19 nucleic acid repositive patients: A literature review

Coronavirus disease 2019 (COVID-19) poses a serious threat to human health and lives. The virus is still spreading throughout the world, and the cumulative number of confirmed cases is increasing. After patients with COVID-19 are treated and discharged, some have repeated clinical symptoms and become positive for nucleic acid tests a second time. Through analysis and review of the existing literature, the proportion of repositive patients in the discharged patient population and their clinical characteristics were systematically described for the first time. Furthermore, an in-depth analysis of the causes of repositive nucleic acid tests and the potential transmission of the disease provides the basis for the management and protection of discharged patients with COVID-19.